time: Add a static TimeTicks method that returns the underlying clock

base/time/time_win.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 
 // Windows Timer Primer
 //
 // A good article:  http://www.ddj.com/windows/184416651
 // A good mozilla bug:  http://bugzilla.mozilla.org/show_bug.cgi?id=363258
 //
@@ skipping 494 matching lines @@
 }
 
 // static
 bool TimeTicks::IsHighResolution() {
   if (g_now_function == &InitialNowFunction)
     InitializeNowFunctionPointer();
   return g_now_function == &QPCNow;
 }
 
 // static
+TimeTicks::Clock TimeTicks::GetClock() {
+  return IsHighResolution() ?
+      Clock::WIN_QPC : Clock::WIN_ROLLOVER_PROTECTED_TIME_GET_TIME;
+}
+
+// static
 ThreadTicks ThreadTicks::Now() {
   DCHECK(IsSupported());
 
   // Get the number of TSC ticks used by the current thread.
   ULONG64 thread_cycle_time = 0;
   GetQueryThreadCycleTimeFunction()(::GetCurrentThread(), &thread_cycle_time);
 
   // Get the frequency of the TSC.
   double tsc_ticks_per_second = TSCTicksPerSecond();
   if (tsc_ticks_per_second == 0)
@@ skipping 82 matching lines @@
 TimeTicks TimeTicks::FromQPCValue(LONGLONG qpc_value) {
   return TimeTicks() + QPCValueToTimeDelta(qpc_value);
 }
 
 // TimeDelta ------------------------------------------------------------------
 
 // static
 TimeDelta TimeDelta::FromQPCValue(LONGLONG qpc_value) {
   return QPCValueToTimeDelta(qpc_value);
 }